Effect of sequencing on combined toxicity of renal irradiation and cisplatin

We are using a rat model to study the effects of sequencing on the combined toxicity of renal irradiation and cisplatin (cis-Pt). Unanesthetized female WAG/RijMCW rats were given bilateral kidney irradiation (20 Gy in 9 fractions), preceded or followed by single ip doses of cis-Pt. Renal irradiation causes an increase in the acute toxicity of cis-Pt given 3-9 months after irradiation. Low-dose cis-Pt given immediately before irradiation, or as long as 9 months after irradiation, causes a decrease in the latent period for radiation nephritis and an increase in its severity. When given 3.7 to 7.7 months prior to irradiation, cis-Pt has a less severe effect on radiation nephritis. The greatest enhancement of radiation nephritis is seen for cis-Pt given 3 months after irradiation. Additive effects of cis-Pt and radiation on renal function can explain much, but not all, of the combined toxicity.     

Chronic effects of fractionated renal irradiation on the pharmacokinetics of intravenous methotrexate

the chronic effects of renal irradiation on the pharmacology of methotrexate was studied in a rat model. Unanesthetized rats received 2 doses of bilateral fractionated kidney irradiation (16.2 Gy or 19.8 Gy in 9 fractions). Alterations in renal function were first seen at 3 months in the 19.8 Gy group and 12 months in the 16.2 Gy groups. Life table analysis showed a shift in the survival curve of about 3 months between the 2 radiation doses. The pharmacokinetics of i.v. methotrexate showed an increase in the area under the plasma curve beginning at 9 months in the 19.8 Gy group and at 15 months in the 16.2 Gy group. The volume of distribution of methotrexate was smaller in the irradiated rats than in unirradiated controls. Multiple linear regression models showed significant correlations between parameters of methotrexate clearance and certain renal function tests. Nevertheless, no set of renal function tests consistently predicted alteration in methotrexate clearance in the 2 radiation groups. Furthermore, time after irradiation remained a highly significant variable indicating that renal irradiation causes time dependent change in methotrexate pharmacokinetics that can not be accounted for by the usual tests of renal function.     

Effect of total-body irradiation with bone marrow transplantation on toxicity of cisplatin

In defined-flora, barrier-maintained rats (WAG/RijMCW males), radiation nephritis is the principal late toxicity seen after high-dose-rate, total-body irradiation (TBI) when hematologic toxicity is prevented by bone marrow transplantation. Pneumonitis develops only if rats are exposed to a conventional environment during and after bone marrow transplantation. Low-dose-rate TBI gives similar toxicity at doses twice as large. Rats surviving for 9 months after TBI show decreased tolerance for cisplatin. This decreased tolerance is related to dose and dose rate and is seen for radiation doses that show little or no renal toxicity. Evidence suggests that the decrease in renal tolerance is due to decreased renal platinum clearance in the irradiated kidneys.     

Tolerance of previously irradiated mouse kidneys to cis-diamminedichloroplatinum(II)

In this study the tolerance of previously irradiated kidneys to retreatment with chemotherapy was assessed. cis-Diamminedichloroplatinum(II) (c-DDP) was given to groups of mice at 1, 3, or 6 months after bilateral renal irradiation with single doses of 8-14 Gy. Renal function was measured monthly (by clearance of 51Cr ethylenediaminetetraacetic acid) from 4-35 weeks after c-DDP injection and results were compared with function after X-rays alone or drug alone. At early testing times (during the first 11 weeks after c-DDP injection) the renal function of mice given drug at 1 or 3 months after irradiation was very similar to that seen after drug alone. c-DDP given at 6 months caused slightly more damage than either drug or X-rays alone, but these results could be explained in terms of additive toxicities. At later testing times (11-35 weeks after c-DDP injection), renal function was much worse in all animals which had received previous irradiation, with the greatest damage when c-DDP was given 6 months after X-rays. This may be partly due to additional cell killing by the drug causing the expression of subclinical radiation injury. It is also possible that c-DDP pharmacokinetics was altered in animals with previously irradiated kidneys, leading to higher drug exposures in these mice.     

Effects of single-dose and fractionated cranial irradiation on rat brain accumulation of methotrexate

The effects of single-dose and fractionated whole-brain irradiation on brain methotrexate (MTX) has been studied in a rat model. The amount of MTX present in the brain 24 hr after a single i.p. dose (100 mg/kg) was the same wether animals were sham irradiated or given a single dose of 2000 rads 6 or 48 hr prior to the drug (6.9, 8.3, and 6.8 pmol MTX/g, wet weight, respectively). Animals sham irradiated or given 2000 rads in 10 fractions over 11 days and treated with an average dose of 1.2 mg MTX/kg i.p. twice a week for 24 weeks did not differ significantly in their brain MTX concentration (7.9 and 8.3 pmol MTX/g, wet weight, respectively). Chronically MTX-treated animals became folate deficient whether they were irradiated or not (450 and 670 pmol folate/g, wet weight, brain in MTX-treated and control animals). Thus, MTX accumulates in the brain with acute or chronic administration, and this accumulation is not altered by this amount of brain irradiation.     

The relative biological effectiveness of fast neutrons (42MeVd→Be) for early and late normal tissue injury in the pig

Early and late radiation damage has been investigated in a number of normal tissues in the pig after irradiation with single doses of neutrons produced by 42MeV deuterons on beryllium. The results have been compared with data obtained after irradiation with single doses of 250kV X rays. In the skin a low RBE value of approximately 1.2 was obtained for the early (3–9 week) epithelial reaction. For the subsequent dermal vascular response, higher RBE values in the range of 1.35–1.6 were obtained; the RBE decreasing with an increase in the neutron dose. For late skin damage, assessed by the relative reduction in the linear dimensions of an irradiated field, a RBE value of approximately 1.5 was obtained. In the kidney the RBE value, for a neutron dose level (550 ecy) at which renal function was just preserved, was 2.0. A lower value of 1.7 was found for doses resulting in a loss of renal function. The results of ¹³³Xenon clearance studies showed two waves of impaired ventilation function in the irradiated lung. In the acute reaction (3–9 months), at a dose level consistent with just preserving normal ventilation function, the RBE value was <1.2. For late lung damage (15–24 months) the R BE value was higher, 1.4. For the rectum, methods are presently only available for assessing acute damage. A RBE of 2.0 was found for neutron doses in the range 350–575 cGy. The RBE values for early endpoints in the skin, lung and gut of the pig are comparable with those published previously for other species, including man. The values for late effects in pig skin and lung were higher than for early damage in those tissues.     

Radiation, methotrexate, and white matter necrosis: laboratory evidence for neural radioprotection with preirradiation methotrexate

To investigate the interactions between methotrexate (MTX) and irradiation of the central nervous system, adult rats were infused with MTX via the lateral cerebral ventricle either before, during, or following single fraction irradiation to the cervical spine. Single doses ranging from 1600 cGy to 3200 cGy were administered and the dose-response curve for forelimb paralysis was compared with that seen in irradiated animals which did not receive MTX. There was no effect on the dose-response curve when MTX was administered simultaneously with or following irradiation compared to radiation alone. When MTX was given prior to irradiation, however, the entire dose-response curve shifted in the direction of radioprotection by approximately 225 cGy. Histopathologic examinations were consistent with this observation, with animals pretreated with methotrexate demonstrating significantly less white matter necrosis than observed in untreated controls. Protection of normal CNS tissue from radionecrosis, and from the associated paralysis, may be achieved with preradiation methotrexate.     

Pilot study of local hyperthermia,radiation therapy,etanidazole, and cisplatin for advanced superficial tumours

Five patients (six hyperthermia sites) with advanced superficial tumours were treated with combined etanidazole, cisplatin, local hyperthermia, and radiation therapy as part of a Phase I pilot study. Treatment was given once weekly and consisted of etanidazole 3 gm/m² IV bolus, cisplatin 50 mg/m² IV bolus, hyperthermia for 60 min with a target temperature of 43°C, and radiation therapy 500 cGy/fraction (median total dose 3000 cGy) for a total of six weeks. Blood levels of etanidazole were taken during treatment at week 1 and week 4. Etanidazole drug exposure was calculated using the trapezoidal rule and expressed as the area under the curve (AUC) of plasma concentration X time. Five of six treatment sites had received prior irradiation. Prior chemotherapy had been given in three patients and tamoxifen therapy given in the other two patients. The median follow-up time is 34 months; 3/5 patients have died of disease. The most significant toxicity was grade I or II nausea and vomiting associated with 19/32 treatments (59%) and a second degree burn in 2/6 fields. None of the five patients experienced peripheral neuropathy, skin ulceration, or needed surgical repair. In addition, there was mild renal toxicity; pharmacokinetic analysis showed a 28–75% increase in the week 1 to week 4 AUC in three patients, all of whom had a decrease in creatinine clearance over the same time of 15–47%. This pilot study suggests this combined modality therapy can be delivered without major complications and that renal function, determined by creatinine clearance, affects clearance of etanidazole and alters the AUC. Therefore, monitoring renal function is important in patients receiving etanidazole in addition to other nephrotoxic agents such as cisplatin. The impact of etanidazole on the therapeutic index of hyperthermia, radiation therapy and cisplatin may be worthy of study, especially since a positive interaction between these modalities is found in laboratory models.     

Analysis of treatment of childhood leukaemia. V. Advantage of reduced chemotherapy during and immediately after cranial irradiation.

This paper compares anti-leukaemic efficiency with toxicity to the patient of chemotherapy during and immediately after central nervous system irradiation. The drug regimen consisted of daily mercaptopurine (MP) and weekly methotrexate (MTX) at the maximum tolerated dose. Of 140 patients with acute lymphoblastic leukaemia allocated to receive this drug regimen during and after cranial irradiation, 8 died in complete remission within 6 months of the end of irradiation. Details of the nature of these deaths are given. This result led the Working Party to modify the chemotherapy scheduled for this stage in treatment. The modified chemotherapy consisted of MP at reduced dosage before and during cranial irradiation and omission of MP and MTX for 3 weeks after irradiation, during which time daily prednisolone with 2 doses of vincristine were substituted. Following that, the treatment reverted to the original schedule of daily MP and weekly MTX at maximum tolerated dose. Of 109 patients allocated to this modified regimen only one died in remission within 24 weeks after cranial irradiation. Analysis of the anti-leukaemic effect of the modified regimen showed that up to 600 days it was at least as effective as the original more intensive regimen. We conclude that there is a definite advantage in keeping chemotherapy to a minimum during and immediately following cranial prophylactic irradiation.     

Methotrexate-vindesine association in the treatment of head and neck cancer Influence of vindesine on methotrexate's pharmacokinetic behavior

Summary Determination of methotrexate (MTX) kinetics after an IV bolus (50 mg/m²) allows prediction of the steady-state plasma level of this drug during a constant infusion. This prediction allows high-dose MTX (HD-MTX) therapy without major toxicity.Patients with head and neck carcinoma received HD-MTX and vindesine (VDS) infusions concomitantly. The therapeutic survey of these patients showed that the predicted plasma level of MTX was not achieved in the presence of VDS. Moreover, the computed dose of MTX had to be increased by a larger amount if the MTX plasma clearance after the identification IV push was low (<9 l/h).In the presence of VDS, the creatinine clearance is lower than when MTX is infused alone, and MTX renal elimination is identical (MTX or MTX+VDS infusions). Thus it seems that the decrease of the MTX plasma level during MTX-VDS infusion could be due to an increase of cellular incorporation.     

Effects of irradiation on malignant cell cytoplasm

Walker-256 carcinoma was transplanted subcutaneously in the dorsum of male Sprague-Dawley rats weighing 100 to 120 gm. The tumors were allowed to grow to 1 cm in diameter. The animals were divided into experimental and control groups. The tumors in the experimental animals were irradiated shielding the rest of the animals, the dose ranging from 50 to 2,000 rads. Specimens were dissected from the irradiated tumors at intervals of 1, 2, 4, 12, 24, and 48 hours, and one week and two weeks after irradiation, and from the control animals at the same intervals. Light microscopy showed no cytoplasmic changes in the irradiated group when the dose was less than 500 rads. With 1,000- and 2,000-rad doses the nuclear profile changed and cytoplasmic basophilia was diminished. Enzyme histochemical studies showed diminution of succinic dehydrogenase and coenzyme I and II as the dose was increased to 2,000 rads, starting 24 hours after irradiation, with marked diminution on the seventh day. The hydrolytic enzyme activities were not altered with a dose up to 1,000 rads. With a 2,000-rad dose, diminution of acid phosphatase activity was seen one week after irradiation. The cytoplasm of the tumor cells in the irradiated group showed diminution in the mitochondrial and microsomal population, most marked when the dosage was increased to 2,000 rads, and one week after irradiation. On the basis of our results it can be proposed that radiosensitivity of a malignant cell in an experimental system is largely dependent on the cytoplasmic organelles.     

Intracavitary therapy of murine ovarian cancer with cis-diamminedichloroplatinum(II) and 10-ethyl-10-deazaaminopterin incorporating systemic leucovorin protection

Administration i.p. of 10-ethyl-10-deazaaminopterin (10EDAM) with cis-diamminedichloroplatinum(II) (cis-Pt) had significant antitumor activity against the murine ovarian tumor. This tumor is a teratoma originating in the ovary with pathogenesis and metastatic properties similar to those of human ovarian cancer. Drug was given on a schedule of once every 3 days for 3 doses 1 or 2 days after i.p. implant of 10(7) tumor cells. Despite the 2-fold attenuation of dosage required, antitumor activity of the combination (increased life span, 161%) was approximately twice that obtained with maximum tolerated doses of either agent alone and tumor-free, long-term survivors were obtained. Incorporation of s.c. calcium leucovorin administration 16 h after each dose of 10EDAM and cis-Pt allowed a 4-fold increase in dosage of 10-EDAM without an increase in toxicity, increased median survival by an additional 120%, and quadrupled the number of tumor-free, long-term survivors to 40% of treated animals. By comparison, methotrexate was only modestly active against this tumor model either as a single agent, with cis-Pt, or with delayed s.c. calcium leucovorin administration. These results appear to suggest that 10EDAM with cis-Pt may have considerable potential for intracavitary therapy of human cancer, including ovarian carcinoma, particularly when incorporating delayed systemic calcium leucovorin administration.     

The effects of dose-fractionation on radiation-induced heart disease in rats

The hearts of Wistar rats were irradiated locally with a range of total doses given in 1, 3, 5 or 10 fractions in 4 weeks. As even after the lowest single dose of 17.5 Gy all animals died within 18 months after irradiation from heart failure, no ED50 could be determined. Therefore, the mean survival time following irradiation was chosen as isoeffect for the comparison of different treatment groups. Fractionation has a marked sparing effect on the radiation-induced heart disease. For an isoeffect of a mean survival time of 42 weeks an alpha/beta of 1 Gy was found.     

Radiation Effects in the Colon: An Experimental Study in the Rat

In an experimental study, resembling a clinical trial of preoperative irradiation, 10 + 10 Gy was given to the pelvic and lower abdominal region of rats with a 4-day interval. The early effect on the colonic wall was evaluated by myeloperoxidase activity and hydroxyproline content of the bowel wall and correlated to histological findings. Groups of animals were followed up to eight months after irradiation for evaluation of later effects. General effects of irradiation were seen as low WBC during the first week and delayed body weight development up to two months after irradiation. Local effect in the colonic wall was noted as an increase in myeloperoxidase activity (indicating a leucocyte accumulation) in irradiated parts of colon during the first 11 days and again significantly elevated after two months in parts of colon, irradiated as well as protected. This correlated well with histological findings of inflammatory reaction, atypia and dysplasia during the first 10 days after irradiation but not at two months after irradiation. Hydroxyproline content was not affected. There were no major complications due to irradiation seen in the late course of the study period.     

Methotrexate pharmacokinetics in infants with acute lymphoblastic leukemia

Purpose We performed a pharmacokinetic evaluation of methotrexate (MTX) in infants with acute lymphoblastic leukemia enrolled on the Pediatric Oncology Group (POG) 9407 Infant Leukemia Study to evaluate the effects of age on MTX pharmacokinetics and pharmacodynamics. Methods A pharmacokinetic database of 61 patients was developed by combining MTX data obtained from 16 patients in a pharmacokinetic sub-study with data obtained for clinical care in other patients enrolled on the POG 9407 protocol. The data were analyzed for the first dose of MTX given to patients in induction/intensification therapy. Patients received MTX (4 g/m²) over 24 h at week 4 of therapy. Toxicity data were also reviewed to evaluate the incidence of common MTX toxicities during the first 6 weeks of therapy (the induction/intensification phase). Results Steady-state clearance (mean ± standard deviation) for infants aged 0–6 months was 89 ± 32 ml/min/m² compared to 111 ± 40 for infants aged 7–12 months (P = 0.030). In the subgroup of infants aged 0–3 months the mean steady-state clearance was 84 ± 30 ml/min/m² (P = 0.026 vs. the 7–12-month group). The incidence of renal toxicity (all grades) during induction/intensification therapy was 23% in the 0–3 months age group compared to 0% (for n = 27) in the group 7–12 months of age (P = 0.029). There were no significant differences in hepatoxicity or mucous membrane toxicity between age groups. Conclusions A modest difference in steady-state MTX clearance is observed between younger infants (0–6 months) and older infants (7–12 months). Very young infants (0–3 months) also experienced a slightly higher incidence of renal toxicity during induction/intensification therapy. Steady-state clearance for the older infants is similar to values reported for children in other studies.     

Influence of nephrotoxic drugs on the late renal toxicity associated with bone marrow transplant conditioning regimens

The total body irradiation that is given as part of bone marrow transplant conditioning regimens is a factor in the renal toxicity that is observed after bone marrow transplant, but it may not be the only factor. We hypothesize that nephrotoxic drugs used in prior chemotherapy can precipitate renal radiation damage. Studies were designed to determine if nephrotoxic antineoplastic drugs could shorten the latent period for the development of radiation nephritis. Rats were given bilateral renal irradiation using a radiation schedule that produced moderate nephritis. Cisplatinum, BCNU, or mitomycin were given before, during, or after irradiation at doses that produced only mild nephrotoxicity. All cisplatinum-radiation sequences resulted in decreased renal function, with radiation prior to cisplatinum producing the greatest dysfunction. BCNU increased renal dysfunction equally in all schedules, but mitomycin had only minimal effects. Most drug schedules, including those with mitomycin, produced earlier development of morbidity after fractionated renal irradiation. In a second set of studies, rats were given single doses of the same nephrotoxic drugs, followed 3 months later by total body irradiation plus bone marrow transplant. The drugs had no effect on the marrow ablation dose, but BCNU and cisplatinum decreased gastrointestinal tolerance. Four months after total body irradiation, rats which received drugs alone or total body irradiation alone have essentially normal renal function, but rats which received cisplatinum plus total body irradiation or BCNU plus total body irradiation show a dose-dependent decrease in renal function. These studies show that radiation nephritis can be precipitated by low doses of nephrotoxic drugs, and may help to explain the incidence of early radiation nephritis in bone marrow transplant patients conditioned with total body irradiation.     

Carboxypeptidase-G2 rescue in cancer patients with delayed methotrexate elimination after high-dose methotrexate therapy

High-dose methotrexate (HDMTX) is a component of many cancer treatment regimens. Despite careful management, delayed renal clearance, followed by extremely high serum levels with potentially life-threatening toxicity can occur. In the present study, we report our results of carboxypeptidase-G2 (CPDG2) rescue in 8 patients with delayed methotrexate elimination and renal impairment after HDMTX therapy for lymphoma or osteosarcoma. A dose of 50 U/kg CPDG2 was administered. MTX plasma levels decreased rapidly and recovery of renal function was observed in all patients. No patient developed severe WHO grade 4 MTX toxicity. CPDG2 provides an alternative route of MTX elimination by converting it to inactive and non-toxic metabolites. CPDG2 rescue was well tolerated, safe and very effective in preventing severe or life-threatening MTX toxicity.     

Bladder damage in mice after combined treatment with cyclophosphamide and X-rays. The influence of timing and sequence

The response of the mouse bladder to single doses of cyclophosphamide (CY), X-rays, or their combination was assessed from the development of functional damage (haematuria and increased frequency of urination). For the combined treatments, a single dose of CY (100 mg.kg-1) was given immediately before or at intervals of up to 9 months before irradiation, or at one week to 9 months after irradiation. Damage after X-rays alone was expressed late, with no functional changes earlier than 5 months. CY alone, by contrast, caused a marked increase in urination frequency and haematuria within one week. There was subsequently partial recovery although some residual damage persisted for at least one year. CY given before or after X-rays caused an early, X-ray dose-related expression of damage. These results suggest that the drug precipitated some of the latent radiation injury. There was also a second wave of damage after the combined treatments and the response at 9-12 months was always more severe than after X-rays alone. This increased late damage could be explained in terms of additive drug and radiation toxicities. Since drug given up to 9 months before or after irradiation caused more severe bladder damage than X-rays alone, CY should be avoided in clinical situations where the bladder has been irradiated.     

Acceleration of late radiation damage of the kidney by unilateral nephrectomy.

Both increased proliferation as measured by labeling index and the appearance of abnormally large nuclei in renal proximal tubule cells, which have been observed in mouse kidneys after irradiation, were enhanced by subsequent unilateral nephrectomy. Nephrectomy alone induced only a transient increase in labeling index, lasting less than 1 month, whereas nephrectomy after irradiation induced an increase above that of the irradiated kidneys without nephrectomy lasting as long as 9 months. The incidence of large nuclei in kidneys from mice unilaterally nephrectomized 1 week after irradiation showed a rapid increase with time, peaking at 4.6% at 6 months, compared to more gradual increases with peaks at about 4.0% at 9 or 12 months in irradiated kidneys without nephrectomy or those in which nephrectomy was done prior to irradiation. This result demonstrates that nephrectomy after irradiation accelerates the appearance of this indicator of radiation damage, rather than enhancing the maximum amount of damage. Unilateral nephrectomy after irradiation also increased kidney damage 9 months later, as indicated by kidney weight loss and increased blood urea nitrogen. These results are consistent with our model for radiation damage of the kidney in which radiation induces cell proliferation and the appearance of reproductively dead, large nuclear cells that are lost at subsequent attempts to divide; the acceleration of radiation damage by unilateral nephrectomy performed after radiation could very well be a result of nephrectomy-induced enhancement in the proliferation of proximal tubule cells.     

Biochemical and pharmacological consequences of the interaction between methotrexate and ketoprofen in the rabbit

Severe methotrexate (MTX) toxicity is a proven complication of associations of MTX and non-steroidal anti-inflammatory drugs (NSAIDs). This study investigated the interaction between MTX (50 or 100 mg kg-1) and ketoprofen (KP) (3 mg kg-1 day-1, pretreatment for 8 days) in the rabbit. The drug association induced a reversible increase in blood urea and creatinine. The severity degree of renal dysfunction was significantly related to the MTX dose; it was not modified by prolonged exposure to KP after MTX administration. The biological markers of haematopoietic and hepatic functions were unchanged. Pretreatment by KP induced a marked reduction (70%) in the urinary excretion of the prostaglandin 6-keto-PGF1 alpha. MTX dose-related alterations in MTX pharmacokinetics were also observed with the drug association: at a MTX dose of 100 mg kg-1, the presence of KP significantly reduced the total body clearance, the renal clearance and the fraction of MTX eliminated in urine as compared to controls. An appreciable reduction in the plasma binding of MTX was also noted in vivo when KP was associated. This experimental study confirms the existence of an interaction between MTX and KP and demonstrates its renal origin.